A federal judge has ruled that Iowa State University violated the free speech rights of student members of a pro-marijuana student group by barring them from using a university logo on T-shirts.

Judge James Gritzner on Friday granted members of the National Organization for the Reform of Marijuana Laws a permanent injunction. It means ISU administrators cannot use a trademark policy to prevent the organization from printing shirts depicting a marijuana leaf.

Former presidents of the group Erin Furleigh and Paul Gerlich sued in July 2014 alleging ISU withdrew approval of a marijuana-themed T-shirt featuring the school's Cy mascot under pressure from donors and lawmakers.

A spokesman for the attorney general's office says ISU is reviewing options including an appeal.